DOCSLIB.ORG

The First Report on Chemoselective Biguanide-Catalyzed Henry Reaction Under Neat Conditions

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The First Report on Chemoselective Biguanide-Catalyzed Henry Reaction Under Neat Conditions 3640 Bull. Korean Chem. Soc. 2012, Vol. 33, No. 11 Abdolhamid Alizadeh et al. http://dx.doi.org/10.5012/bkcs.2012.33.11.3640 The First Report on Chemoselective Biguanide-Catalyzed Henry Reaction under Neat Conditions Abdolhamid Alizadeh,†,‡,* Mohammad M. Khodaei,†,‡,* Gisya Abdi,† and Davood Kordestani† †Department of Organic Chemistry, Faculty of Chemistry, Razi University, Kermanshah 67149, Iran ‡Nanoscience & Nanotechnology Research Center (NNRC), Razi University, Kermanshah 67149, Iran *E-mail: ahalizadeh2@hotmail.com (A. Alizadeh); mmkhoda@razi.ac.kr (M.M. Khodaei) Received May 23, 2012, Accepted August 11, 2012 An efficient synthetic method for direct Henry reaction catalyzed by a biguanide; namely metformin, as an organosuper-base, between a variety of aromatic and aliphatic aldehydes and nitromethane under neat conditions has been developed. Convenient procedure for removal of the catalyst, chemoselective acquiring of β-nitroalcohols as predominant products, as far as possible short reaction time with excellent conversions are advantages of the developed protocol. Key Words : Organosuper-base catalysts, Henry reaction, Nitroaldol reaction, Biguanides, Metformin Introduction dines and guanidines, have been attracting much attention in organic synthesis due to their potential functionality.10a-d One One of the main purposes in organic chemistry is carbon- of the important and beneficial characteristics of an organic carbon bond formation and in this regard, the Henry base, especially from the view point of environmental as- reaction1 (an aldol-type C-C bond formation; called nitro- pects, is the ability of recycling use in repeated reactions, in aldol reaction) has been used extensively in many important which reversible proton transfer occurs between the base synthetic strategies.2 This reaction simply takes places with and a substrate as an acidic counterpart. Thus, powerful the help of basic organic,3-5 inorganic catalysts6 or quaternary organic bases that may be applicable in various organic ammonium salts.7 These catalysts often result in side reac- syntheses as basic catalysts have attracted much attention. tions such as aldol-condensation, Cannizzaro reaction,8 Biguanides with a dual guanidine-like moiety are interest- nitroalkene formation, Michael reactions, retro-aldol reac- ing class of organosuper-bases in which their basicity is due tion1 and Nef reaction.9 Therefore the development of new to the construction of a highly effective conjugation system catalysts for the Henry reaction to avoid these side reactions after protonation under reversible conditions; primitively, it and likewise produce nitroalchohols chemoselectively in is a reflection of the number of canonical forms, especially short time, under mild conditions and using inexpensive and isoelectronic forms, in the resonance system (Scheme 1). less toxic solvent is highly desirable. Generally, biguanides that contain three amino groups are Recently, nitrogen-containing organobases, such as ami- stronger bases than guanidines and amidines that have two Scheme 1. Structures of amidines, guanidines and biguanides. The number of canonical forms, in the resonance system of protonated metformin constructs a highly effective conjugation system. The First Report on Chemoselective Biguanide-Catalyzed Henry Reaction Bull. Korean Chem. Soc. 2012, Vol. 33, No. 11 3641 and one amino groups, respectively.11 To the best of our Table 1. Optimization of the reaction condition knowledge, whereas nitro-aldol reaction has been well studied with amines,3 amidines4 and guanidines,5 there is no report on employing the biguanides in nitro-aldol reaction. In this study, for the first time, we have utilized metformin, Cat. CH3NO2 Time Conversion/NMR an easily available biguanide and very strong organosuper- Entry Solvent base, to catalyze the Henry reaction of a variety of aliphatic, (mmol %) (equiv) (h) yield (%) aromatic and heteroaromatic aldehydes with nitromethane at 1- 2 -240 room temperature without addition of stoichiometric amount 2102 - 2 85 of the base. 3 5 2 - 1 100/100 42 2 -2 45 Results and Discussion 55 1 -2 50 6104 - 2 90 Our investigations on the chemoselective synthesis of 75 2H2O2450 nitroalcohols from various aldehydes and nitromethane as a 85 2EtOH2450 pro-nucleophile in the presence of catalytic amount of met- 95 2CH3CN 24 60 formin, began with the optimization of the reaction condi- 10 5 4 H2O2460 tions. The synthetic pathway is shown in Scheme 2. Our initial examination was involved to investigate the reaction of 2,4-dichlorobenzaldehyde with nitromethane in nitroalkene, aldol-condensation, Cannizzaro and Nef reac- various conditions. Table 1 lists the representative data tions. obtained for the synthesis of 2-nitro-1-(2,4-dichlorophenyl)- With a reliable set of conditions in hand, and in order to ethanol under various experimental conditions. The reaction investigate the utility of metformin as an appropriate basic mixture was stirred at room temperature and the progress catalyst in Henry reaction, we also probed the scope and was monitored by TLC. A control experiment in the absence generality of the reaction of several aryl and alkyl aldehydes of metformin (Table 1, entry 1) showed no evidence of with a variety of functionalities (Table 2). As shown in Table nitroalcohol formation confirming the basic role of met- 2, β-nitroalcohols were obtained in good to excellent con- formin as the organosuper-base catalyst in the described versions and the yields of the desired Henry products were transformation. estimated using the crude 1H NMR spectra. In addition, various amounts of metformin were added It was found that aromatic aldehydes with electron-with- under the mentioned conditions. Among different amounts drawing groups in reaction with nitromethane give the of the catalyst and nitromethane (Table 1, entries 2-6), the desired products with excellent conversions (Table 2, entries best results were achieved when the reaction was performed 2-5). When the reaction was performed with halo-benz- with 5 mol % of catalyst and 2 equiv. of nitromethane to aldehydes (Table 2, entries 6-10), the corresponding 2-nitro- give 100% conversion of the starting materials to the related alcohols were obtained in good to excellent conversions β-nitroalcohol product (Table 1, entry 3) and the crude 1H ranging from 82% to 100%. Although aldehydes with elec- NMR spectrum was employed to estimate yield of the desir- tron-donating groups are more unfavorable to react rather ed Henry product which was ~100%. In addition, various than those with electron-withdrawing groups however they solvents were employed for the aforementioned reaction gave the desired products in high to excellent conversions (Table 1, entries 7-10) and high conversion was observed (Table 2, entries 11-13) which showed that the nature of the using nitromethane as neat conditions without the presence substitutions on the ring did not significantly hamper the of solvent. Hence, the optimized conditions found for the reaction. synthesis of 2-nitroalcohols starting from aldehyde and In addition, reaction of di-aldehydes such as iso- and nitromethane are the use of 1 equiv. of aldehyde, 2 equiv of terephthalaldehyde with nitromethane under the developed nitromethane in the presence of 5 mol % of metformin at conditions led to the related di-β-nitroalcohols (Table 2, room temperature stirring for 1 h under aerobic conditions. It entries 14, 15) through double cascade Henry reactions. is worthy to mention that 1H NMR studies showed no Interestingly, heteroaromatic aldehydes reacted with the evidence of by-product formation resulting from typical side nitromethane and gave their related β-nitroalcohols with reactions such as dehydration of the 2-nitroalcohol into 100% conversions (Table 2, entries 16, 17). Due to the possible self-condensation reaction of aliphatic aldehydes, they seem to be less reactive in Henry reaction. Notably, under the developed protocol the biguanide-type catalyst was capable of catalyzing the Henry reaction of an aliphatic aldehyde with nitromethane and chemoselective acquiring of β-nitroalcohols in high to excellent conversions Scheme 2. Henry reaction of nitromethane with carbonyl compounds (Table 2, entry 18). catalyzed with metformin under neat condition. The scope of the developed procedure was more expand- 3642 Bull. Korean Chem. Soc. 2012, Vol. 33, No. 11 Abdolhamid Alizadeh et al. Table 2. Henry reaction between various aldehydes (1 mmol) and nitromethane (2 mmol) using 5 mol % of catalyst at room temper- ature for 1 h Conversion NMR Yield Entry Aldehyde (%) (%) 1 100 ~ 100 b Scheme 3 2100− ed, especially on ketone substrates. In order to evaluate the 3100b − possible catalytic activity of biguanide in the Henry reaction of ketones, we probed the reaction of various aliphatic, aromatic, and aryl-alkyl ketones with nitromethane. Among 4100b − the studied ketones, only cyclohexanone showed the excellent reactivity in short time (Table 2, entry 19) while 595− acetone, acetophenone and benzophenone failed to give the desired products under the developed condition (Table 2, 69590entries 20-22) possibly due to the preferential self-condensa- tion reaction or retro-Henry reaction.12 The Henry reaction with ketones is sensitive to steric factors and generally gives 7 100 100 a complex mixture of products depending on the ratio of reactants, base, temperature and time. 88888To provide more experimental supports for the above- mentioned chemoselectivity, we mixed 1 mmol of acetone,
Load more

Recommended publications
  • (Nitroaldol) Reaction
    MICROREVIEW DOI: 10.1002/ejoc.201101840 Biocatalytic Approaches to the Henry (Nitroaldol) Reaction Sinéad E. Milner,[a] Thomas S. Moody,[b] and Anita R. Maguire*[c] Keywords: Enzyme catalysis / Biocatalysis / C–C coupling / Nitroaldol reaction / Nitro alcohols Enantiopure β-nitro alcohols are key chiral building blocks approaches to the Henry (nitroaldol) reaction. The first for the synthesis of bioactive pharmaceutical ingredients. method is a direct enzyme-catalysed carbon–carbon bond The preparation of these target compounds in optically pure formation resulting in either an enantio-enriched or enantio- form has been the focus of much research and there has been pure β-nitro alcohol. The second approach describes the an emergence of biocatalytic protocols in the past decade. Henry reaction without stereocontrol followed by a biocata- For the first time, these biotransformations are the focus of lytic resolution to yield the enantiopure β-nitro alcohol. this review. Herein, we describe two principal biocatalytic Introduction The construction of carbon–carbon bonds is an essential element of synthetic organic chemistry. Among the various C–C bond forming reactions, the nitroaldol or Henry reac- tion[1] is one of the classical named reactions in organic synthesis. Essentially, this reaction describes the coupling of a nucleophilic nitro alkane with an electrophilic aldehyde or ketone to produce a synthetically useful β-nitro alcohol (Scheme 1).[2–5] Moreover, the Henry reaction facilitates the joining of two molecular fragments, under mild reaction conditions with the potential formation of two new ste- reogenic centres and a new C–C bond. The resulting β-nitro alcohols can undergo a variety of useful chemical transfor- mations which lead to synthetically useful structural motifs, e.g.
    [Show full text]
  • Green Chemistry – Aspects for the Knoevenagel Reaction
    2 Green Chemistry – Aspects for the Knoevenagel Reaction Ricardo Menegatti Universidade Federal de Goiás Brazil 1. Introduction Knoevenagel condensation is a classic C-C bond formation reaction in organic chemistry (Laue & Plagens, 2005). These condensations occur between aldehydes or ketones and active methylene compounds with ammonia or another amine as a catalyst in organic solvents (Knoevenagel, 1894). The Knoevenagel reaction is considered to be a modification of the aldol reaction; the main difference between these approaches is the higher acidity of the active methylene hydrogen when compared to an -carbonyl hydrogen (Smith & March, 2001). Figure 1 illustrates the condensation of a ketone (1) with a malonate compound (2) to form the Knoevenagel condensation product (3), which is then used to form the ,-unsaturated carboxylic compounds (3) and (4) (Laue & Plagens, 2005). R R R O O O O H O O O + base hydrolysis H O O O O R R (1) (2) (3) (4) Fig. 1. An example of the Knoevenagel reaction. Subsequent to the first description of the Knoevenagel reaction, changes were introduced using pyridine as the solvent and piperidine as the catalyst, which was named the Doebner Modification (Doebner, 1900). The Henry reaction is another variation of the Knoevenagel condensation that utilises compounds with an -nitro active methylene (Henry, 1895). The general mechanism for the Knoevenagel reaction, which involves deprotonation of the malonate derivative (6) by piperidine (5) and attack by the formed carbanion (8) on the carbonyl subunit (9) as an aldol reaction that forms the product (10) of the addition step is illustrated in Fig.
    [Show full text]
  • Nitroalkanes As Central Reagents in the Synthesis of Spiroketals
    Molecules 2008, 13, 319-330 molecules ISSN 1420-3049 © 2008 by MDPI www.mdpi.org/molecules Review Nitroalkanes as Central Reagents in the Synthesis of Spiroketals Roberto Ballini 1,*, Marino Petrini 1 and Goffredo Rosini 2 1 Dipartimento di Scienze Chimiche, Università di Camerino, via S.Agostino, 1, I-62032 Camerino, Italy; E-mail: marino.petrini@unicam.it. 2 Dipartimento di Chimica Organica ‘A. Mangini’, Alma Mater Studiorum–Università di Bologna, Viale del Risorgimento n. 4, 40136 Bologna, Italy; E-mail: goffredo.rosini@unibo.it. * Author to whom correspondence should be addressed; E-mail: roberto.ballini@unicam.it; Fax: +39 0737 402297 Received: 8 January 2008; in revised form: 2 February 2008 / Accepted: 4 February 2008 / Published: 7 February 2008 Abstract: Nitroalkanes can be profitably employed as carbanionic precursors for the assembly of dihydroxy ketone frameworks, suitable for the preparation of spiroketals. The carbon-carbon bond formation is carried out exploiting nitroaldol and Michael reactions, while the nitro to carbonyl conversion (Nef reaction) ensures the correct introduction of the keto group. Several spiroketal systems endowed with considerable biological activity can be prepared using this synthetic strategy. Keywords: Conjugate addition, Nef reaction, nitroaldol reaction, nitroalkanes, spiroketals. 1. Introduction The spiroketal moiety is a key motif embodied in a large number of natural products present in plants, fungi, insect secretions, shellfish toxins and other living organisms [1-5]. Many of these compounds also display a considerable biological activity as antibiotics and pheromones. From a synthetic standpoint, among various practical strategies currently available for the assembling of the spiroketal unit, the one based on the acid promoted intramolecular acetalization of dihydroxy ketone derivatives 1 firmly occupies a prominent position (Scheme 1).
    [Show full text]
  • The Development and Use of Chiral 4-Dimethylaminopyridine-N-Oxide As an Organocatalyst
    THE DEVOLOPMENT AND USE OF CHIRAL 4- DIMETHYLAMINOPYRIDINE-N-OXIDE AS AN ORGANOCATALYST A Dissertation Submitted to the Graduate Faculty of the North Dakota State University of Agriculture and Applied Science By Jesse Jo Joyce In Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Major Department: Chemistry and Biochemistry July 2018 Fargo, North Dakota North Dakota State University Graduate School Title The Development and Use of Chiral 4-Dimethylaminopyridine-N-Oxide as an Organocatalyst By Jesse Jo Joyce The Supervisory Committee certifies that this disquisition complies with North Dakota State University’s regulations and meets the accepted standards for the degree of MASTER OF SCIENCE SUPERVISORY COMMITTEE: Mukund Sibi, PhD Chair Gregory Cook, PhD Seth Rasmussen, PhD Yongki Choi, PhD Approved: 11/09/18 Gregory Cook, PhD Date Department Chair ABSTRACT Organocatalysis is a field that has bloomed over the last decades. With the field’s promise of being able to mimic nature and afford products in a synergistic manner to traditional Lewis acid catalysis, several interesting discoveries have been made. Owing to the vastness of the field as it exists today, this document will focus on two main aspects; cinchona alkaloid (and derivatives) as used in common carbon-carbon bond forming reactions and kinetic resolution via 4-dimethyl aminopyridine-N-oxide derivative driven acylation. Kinetic resolution via organocatalysis has the potential to react one enantiomer of a racemic mixture without affecting the other. The highlight of this screening was an s factor of 9 which was produced using optimized conditions using a catalyst designated DMAPO-IV.
    [Show full text]
  • 12.2% 122,000 135M Top 1% 154 4,800
    We are IntechOpen, the world’s leading publisher of Open Access books Built by scientists, for scientists 4,800 122,000 135M Open access books available International authors and editors Downloads Our authors are among the 154 TOP 1% 12.2% Countries delivered to most cited scientists Contributors from top 500 universities Selection of our books indexed in the Book Citation Index in Web of Science™ Core Collection (BKCI) Interested in publishing with us? Contact book.department@intechopen.com Numbers displayed above are based on latest data collected. For more information visit www.intechopen.com Chapter Hydrolase-Catalyzed Promiscuous Reactions and Applications in Organic Synthesis Yun Wang and Na Wang Abstract The potential of biocatalysis becomes increasingly recognized as an efficient and green tool for modern organic synthesis. Biocatalytic promiscuity, a new frontier extended the use of enzymes in organic synthesis, has attracted much attention and expanded rapidly in the past decade. It focuses on the enzyme catalytic activities with unnatural substrates and alternative chemical transformations. Exploiting enzyme catalytic unconventional reactions might lead to improvements in existing catalysts and provide novel synthesis pathways that are currently not available. Among these enzymes, hydrolase (such as lipase, protease, acylase) undoubtedly has received special attention since they display remarkable activities for some unexpected reactions such as aldol reaction and other novel carbon-carbon and carbon-heteroatom bond-forming reactions. This chapter introduces the recent progress in hydrolase catalytic unconventional reactions and application in organic synthesis. Some important examples of hydrolase catalytic unconventional reac- tions in addition reactions are reviewed, highlighting the catalytic promiscuity of hydrolases focuses on aldol reaction, Michael addition, and multicomponent reactions.
    [Show full text]
  • Nitroalkanes As Key Building Blocks for the Synthesis of Heterocyclic Derivatives
    Issue 5th Eurasian Conference on Heterocyclic Chemistry ARKIVOC 2009 (ix) 195-223 Nitroalkanes as key building blocks for the synthesis of heterocyclic derivatives Roberto Ballini* and Marino Petrini Dipartimento di Scienze Chimiche, Università di Camerino, via S. Agostino, 1, I-62032 Camerino, Italy E-mail: roberto.ballini@unicam.it Abstract Nitroalkanes constitute a valuable source of stabilized carbanions for carbon–carbon bond formation through reaction with suitable electrophiles. Reduction of the nitro group or its conversion to a carbonyl group readily provides the necessary amino and oxygenated functions suitable for the preparation of various heterocyclic derivatives. Keywords: Conjugate addition, heterocycles, Nef reaction, nitro-aldol reaction, nitro-alkanes Contents 1. Introduction 2. Lactones 2.1 γ- Lactones 2.2 Macrolactones and dilactones 3. Spiroketals 4. Pyrrolidines and derivatives 4.1 Pyrrolidin-2-ones 4.2 Pyrrolidines and related bicyclic derivatives 5. Piperidines and related derivatives 6. Polyheterocyclic derivatives 7. Conclusions 1. Introduction Cyclic frameworks incorporating one or more heteroatoms in their structures are included in a considerable number of compounds which are of practical interest. The nature of the functional ISSN 1551-7012 Page 195 ©ARKAT USA, Inc. Issue 5th Eurasian Conference on Heterocyclic Chemistry ARKIVOC 2009 (ix) 195-223 groups present in the reactants used for their preparation depends strongly on the attributes of the heterocyclic system. The preparation of oxygen- containing rings usually requires the presence of hydroxy groups in some key step of their synthesis. Similarly, the introduction of nitrogen atoms in cyclic structures can be realized by starting from amino compounds that can, in turn, be obtained by reduction of various nitrogenated derivatives.
    [Show full text]
  • Organocatalytic Asymmetric Assembly Reactions for the Syntheses of Carbohydrate Derivatives by Intermolecular Michael-Henry Reactions
    Organocatalytic asymmetric assembly reactions for the syntheses of carbohydrate derivatives by intermolecular Michael-Henry reactions Hisatoshi Uehara, Ritsuo Imashiro, Gloria Hernández-Torres, and Carlos F. Barbas III1 The Skaggs Institute for Chemical Biology and the Departments of Chemistry and Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037 Edited by David W. C. MacMillan, Princeton University, Princeton, NJ, and accepted by the Editorial Board May 29, 2010 (received for review March 17, 2010) Given the significance of carbohydrates in life, medicine, and indus- organocatalytic approach has been a driving force in the field try, the development of simple and efficient de novo methods to (14, 17–23). synthesize carbohydrates are highly desirable. Organocatalytic Recently, we reported highly selective anti-Michael reactions asymmetric assembly reactions are powerful tools to rapidly of (tert-butyldimethylsilyloxy)acetaldehyde 1 to form γ-nitroalde- construct molecules with stereochemical complexity from simple hydes 4 catalyzed by primary amine-thiourea 3 (24). This type of precursors. Here, we present a simple and robust methodology catalyst provides for enamine-based activation of the aldehyde for the asymmetric synthesis of pyranose derivatives with talo- while enforcing configurational control of enamine geometry. To- and manno- configurations from simple achiral precursors through gether with hydrogen bonding activation of β-nitroalkenes pro- organocatalytic asymmetric intermolecular Michael–Henry reaction vided by the thiourea (25–29) functionality of the catalyst, this sequences. In this process, (tert-butyldimethylsilyloxy)acetalde- catalyst effectively merges two key functionalities in organocata- hyde 1 was successfully utilized in two ways: as a donor in a highly lysis.
    [Show full text]
  • Enzyme-Catalyzed Henry Reaction in Choline Chloride-Based Deep Eutectic Solvents S Xuemei Tian1,2, Suoqin Zhang2, and Liangyu Zheng1*
    J. Microbiol. Biotechnol. (2016), 26(1), 80–88 http://dx.doi.org/10.4014/jmb.1506.06075 Research Article Review jmb Enzyme-Catalyzed Henry Reaction in Choline Chloride-Based Deep Eutectic Solvents S Xuemei Tian1,2, Suoqin Zhang2, and Liangyu Zheng1* 1College of Life Sciences, Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, Jilin University, Changchun 130012, P.R. China 2College of Chemistry, Jilin University, Changchun 130012, P.R. China Received: July 1, 2015 Revised: September 11, 2015 The enzyme-catalyzed Henry reaction was realized using deep eutectic solvents (DESs) as a Accepted: October 5, 2015 reaction medium. The lipase from Aspergillus niger (lipase AS) showed excellent catalytic activity toward the substrates aromatic aldehydes and nitromethane in choline chloride:glycerol at a molar ratio of 1:2. Addition of 30 vol% water to DES further improved the lipase activity First published online and inhibited DES-catalyzed transformation. A final yield of 92.2% for the lipase AS-catalyzed October 6, 2015 Henry reaction was achieved under optimized reaction conditions in only 4 h. In addition, the *Corresponding author lipase AS activity was improved by approximately 3-fold in a DES–water mixture compared Phone: +86-431-85155252; with that in pure water, which produced a final yield of only 33.4%. Structural studies with Fax: +86-431-85155252; fluorescence spectroscopy showed that the established strong hydrogen bonds between DES E-mail: lyzheng@jlu.edu.cn and water may be the main driving force that affects the spatial conformation of the enzyme, S upplementary data for this leading to a change in lipase activity.
    [Show full text]
  • Henry Reaction Between Benzaldehyde and Nitromethane Over Solid Base Catalysts: a Green Protocol
    Green and Sustainable Chemistry, 2018, 8, 139-155 http://www.scirp.org/journal/gsc ISSN Online: 2160-696X ISSN Print: 2160-6951 Henry Reaction between Benzaldehyde and Nitromethane over Solid Base Catalysts: A Green Protocol Magda H. Abdellattif1*, Hany Mahmoud Mohamed2 1Pharmaceutical chemistry department, Deanship of Scientific research Taif University, Taif, KSA 2Chemistry Department, Faculty of Science, Taif University, Taif, KSA How to cite this paper: Abdellattif, M.H. Abstract and Mohamed, H.M. (2018) Henry Reac- tion between Benzaldehyde and Nitrome- The development of environmentally benign solid base catalysts instead of the thane over Solid Base Catalysts: A Green soluble bases for C-C bond formation in organic reactions especially Henry Protocol. Green and Sustainable Chemistry, reactions with nitroalkanes compounds is of intense research activity in the 8, 139-155. https://doi.org/10.4236/gsc.2018.82010 bulk and fine chemical chemistry in order to achieve the selectivity of the de- sired product and the reduction of the salts formed due to soluble bases neu- Received: February 18, 2018 tralization. While using of LDHs catalysts in the synthesis of nitro alcohols is Accepted: April 27, 2018 Published: April 30, 2018 of great interest because LDHs (double layered hydroxides) is of unique properties and an excellent catalytic property. The nitroalcohols are obtained Copyright © 2018 by authors and in a very good yield while using catalyst either by conventional at 90˚C in liq- Scientific Research Publishing Inc. uid phase, microwave or sonoenergy without solvent methods, and the results This work is licensed under the Creative Commons Attribution International yields are compared.
    [Show full text]
  • Aldol Condensation
    CHAPTER‐12 MECHANISM OF REACTION ALDOL CONDENSATION: An aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β‐ hydroxyaldehyde or β‐hydroxyketone, followed by a dehydration to give a conjugated enone. Aldol condensations are important in organic synthesis, providing a good way to form carbon–carbon bonds. The Robinson annulation reaction sequence features an aldol condensation; theWieland‐Miescher ketone product is an important starting material for many organic syntheses. Aldol condensations are also commonly discussed in university level organic chemistry classes as a good bond‐forming reaction that demonstrates important reaction mechanisms. In its usual form, it involves the nucleophilic addition of a ketone enolate to an aldehyde to form a β‐hydroxy ketone, or "aldol" (aldehyde + alcohol), a structural unit found in many naturally occurring molecules and pharmaceuticals. The name aldol condensation is also commonly used, especially in biochemistry, to refer to the aldol reaction itself, as catalyzed by aldolases. However, the aldol reaction is not formally a condensation reaction because it does not involve the loss of a small molecule. The reactions between a ketone and a carbonyl compound lacking an alpha‐Hydrogen(Cross Aldol condensation) is called Claisen‐Schmidt condensation. These reactions are named after two of its pioneering investigators Rainer Ludwig Claisen and J. G. Schmidt, who independently published on this topic in 1880 and 1881. An example is the synthesis of dibenzylideneacetone. MECHANISM: The first part of this reaction is an aldol reaction, the second part a dehydration—an elimination reaction. Dehydration may be accompanied by decarboxylation when an activated carboxyl group is present.
    [Show full text]
  • Synthesis of Optically Pure Nitrogenated Ligands and Their Uses in Asymmetric Catalysis Bilal El Asaad
    Synthesis of Optically Pure Nitrogenated Ligands and their uses in Asymmetric Catalysis Bilal El Asaad To cite this version: Bilal El Asaad. Synthesis of Optically Pure Nitrogenated Ligands and their uses in Asymmetric Catalysis. Catalysis. Université de Lyon; Université libanaise, 2017. English. NNT : 2017LYSE1119. tel-01590361 HAL Id: tel-01590361 https://tel.archives-ouvertes.fr/tel-01590361 Submitted on 19 Sep 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THESIS IN CHEMISTRY For obtention a PhD degree from Claude Bernard - Lyon 1 University and Lebanese University Synthesis of Optically Pure Nitrogenated Ligands and their uses in Asymmetric Catalysis Defended by Bilal EL ASAAD 07 July 2017 Infront of the Jury: Mrs Catherine Pinel, Director of IRCELYON/CNRS, UCBL Examinator Mr. Stéphane Pellet Rostaing, Director of ICMS/CNRS/CEA Reviewer Mr. Kamal Bouhadir, Professor, American University of Beirut Reviewer Mr. Houssam Rassy, Associate Professor, American University of Beirut Examinator Mr. Marc Lemaire, Professor, Lyon1 University, CASYEN-UMR 5246 Supervisor Mr. Iyad Karamé, Professor, Lebanese university, LCOM-FS1 Supervisor Mrs. Estelle Metay, HDR, CNRS/UCBL, CASYEN-UMR 5246 Co-supervisor Mr. Mohammad Jahjah, Professor, Lebanese university Iniv.
    [Show full text]
  • Solvent-Free Aldol Condensation Reactions: Synthesis of Chalcone Derivatives Supplementary Material
    Supplementary information for Comprehensive Organic Chemistry Experiments for the Laboratory Classroom © The Royal Society of Chemistry 2017 Solvent-Free Aldol Condensation Reactions: Synthesis of Chalcone Derivatives Supplementary Material Experiment Notes Instructor Notes 1 Experimental Tips 2 Optional Modifications 3 Figures Experimental photos 4 1H NMR 5 IR spectra 7 Thin-Layer Chromatography (TLC) Analysis 10 Instructor Notes This inquiry-based laboratory features one of the most powerful carbon-carbon bond forming reactions in organic chemistry while highlighting several green and sustainable principles. At the beginning of the experiment, each student obtains an “unknown” benzaldehyde derivative (4-chlorobenzaldehyde, 4-bromobenzaldehyde, or 3-bromobenzaldehyde) to use in the solvent-free aldol condensation. The procedure involves grinding acetophenone with one equivalent of sodium hydroxide and benzaldehyde derivative for ten minutes using a mortar and pestle. Each chalcone is then isolated by suction filtration after washing with water. Although the crude chalcone is often found to have sufficient purity for product characterization, recrystallization is performed with 95% ethanol to remove trace impurities. Once students isolate their product, they use a variety of techniques (melting point determination, thin-layer chromatography (TLC), NMR and IR spectroscopy) in order to determine the identity of their chalcone. This simple experiment is ideal for intermediate organic chemistry students as it is easily and consistently executed in high yield, incorporates problem solving and highlights green chemistry principles as the synthesis minimizes waste production (no reaction solvent) and proceeds with high atom economy. This experiment was designed for CHM 249 (Organic Chemistry) at the Department of Chemistry at the University of Toronto.
    [Show full text]